Distributed Power Generation
Distributed Power Generation = an energy system (mainly) based on interconnected little and medium size power generators and/or renewable energy plants
OR: (can also be understood as home production of solar or other renewable energy)
or: using otherwise unused space to generate solar power
1. Definition by Wikipedia at http://en.wikipedia.org/wiki/Distributed_generation
"Distributed generation generates electricity from many small energy sources. It has also been called also called on-site generation, dispersed generation, embedded generation, decentralized generation, Decentralized Energy or distributed energy." (http://en.wikipedia.org/wiki/Distributed_generation)
See also the Definition by Ezio Manzini at http://sustainable-everyday.net/manzini/?p=9
2. Definition by the Distributed Generation Educational Module:
"Distributed generation is an approach that employs small-scale technologies to produce electricity close to the end users of power. DG technologies often consist of modular (and sometimes renewable-energy) generators, and they offer a number of potential benefits. In many cases, distributed generators can provide lower-cost electricity and higher power reliability and security with fewer environmental consequences than can traditional power generators.
In contrast to the use of a few large-scale generating stations located far from load centers--the approach used in the traditional electric power paradigm--DG systems employ numerous, but small plants and can provide power onsite with little reliance on the distribution and transmission grid. DG technologies yield power in capacities that range from a fraction of a kilowatt [kW] to about 100 megawatts [MW]. Utility-scale generation units generate power in capacities that often reach beyond 1,000 MW." (http://www.dg.history.vt.edu/ch1/introduction.html)
3. Definition in the Appropedia:
"Distributed Generation (DG) is generation of electricity by small-scale power plants located near the electric loads they serve. Distributed generation networks act like peer-to-peer file sharing systems like bit torrent on the internet rather than the primitive internet and conventional grid with few centers of information and energy, respectively. DG is therefore much less susceptible to large-scale power outages caused by natural or the increasing number of manmade disasters that threaten national security." (http://www.appropedia.org/Distributed_generation)
"distributed power generation: This expression usually refers to an energy system (mainly) based on interconnected little and medium size power generators and/or renewable energy plants. Its implications is a radical change in the dominant idea of electrical system. But not only: there is the possibility of a new relationship between communities and their technological assets and, possibly, a more democratic way of managing the energy system.
Today, even if it is not yet the main stream strategy, the option of the distributed generation is largely recognized as a very promising one and its implementation has been enhanced in several different contexts, both in dense urban spaces and in the country side, in the North and in the south of the world. The distributed power option has been made possible thanks to the convergence of several factors as: the existence of highly effective little and medium size power generators and the possibility to base the new energy systems on an intelligent information network." (http://sustainable-everyday.net/manzini/?p=9)
From the Introduction to Distributed Generation:
"Three conceptual models have been envisaged: Micro (or Mini) Grids, Active Networks supported by ICT and an ‘Internet’ model - all of which could have application depending on geographical constraints and market evolution.
Micro-Grids are small electrical distribution systems that connect multiple customers to multiple distributed sources of generation and storage. Micro-grids are typically characterised by multipurpose electrical power services to communities with populations ranging up to 500 households with overall energy demands ranging up to several thousand kWh per day and are connected via low voltage networks. These hybrid systems have the potential to provide reliable power supply to remote communities where connection to transmission supply is uneconomic. A number of demonstration projects have been undertaken in the Greek islands with this type of system.
Active networks are envisaged as a possible evolution of the current passive distribution networks and may be technically and economically the best way to initially facilitate DG in a deregulated market. Active networks have been specifically conjectured as facilitators for increased penetration of DG and are based on a recognition that new ICT technology and strategies can be used to actively manage the network.
The model employs two novel concepts. The first is that the primary role of the network is to provide connectivity. That is the network is a highway system that provides (multiple) links between points of power supply and demand. The second is that the network must interact with the consumer. The current system essentially provides an ‘infinite’ system in that the network itself remains virtually unaffected whatever is happening on the supply or demand side. If a customer requires such a supply then they should pay for this ‘premium’ service.
The structure of this model is based on increased interconnection as opposed to the current mostly linear / radial connections, relatively small local control areas and the charging of system services based on connectivity. The active network has some analogies to telephone networks and requires active management of congestion unlike conventional passive systems that rely on Ohm’s law to determine power routing. With increased distribution of power input nodes due to DG, bi-directional energy flow is possible and new technologies are emerging that can enable direct routing of electricity. New power electronics systems offer ways to control the routing of electricity and also provide flexible DG interfaces to the network. Flexible AC Transmission Systems (FACTS) and Custom Power Devices at lower voltages offer the potential manage routing of power supply in an active manner.
Each node whether a gigawatt natural gas power station or a single solar photovoltaic panel needs to be controlled and the necessary number of combined control tasks multiply. Application of FACTS, or similar technology, increases the number of control parameters. Accurate information on the state of the network and coordination between local control centres is essential using state of the art ICT.
Electricity transmission in the system is not dependent on a single route so failure due to a single component problem is reduced. However an inherent risk of interconnected networks is a domino effect - that is a system failure in one part of the network can quickly spread. Therefore the active network needs appropriate design standards, fast acting protection mechanisms and also automatic reconfiguration equipment to address potentially higher fault levels.
The greatest change in the active network model is at the local control area level where each defined area has its own power control system managing the flow of power across its boundaries. The system would be ICT-based with management enabled by remote actuators controlling the system. The central area control computer would ‘negotiate’ with neighbouring areas on exchange of power. If an area was isolated then the system would react by disconnecting enough load or generation to maintain the correct power balance. This could lead to considerable improvements in the reliability of the supply system as a whole. This model requires relatively little further investment in infrastructure, except to reinforce some areas of the network to provide increased interconnection and investment in automated switch gear.
The internet model effectively takes the active network to the global scale but distributes control around the system. The flow of information around the world wide web/ internet uses the concept of distributed control where each node, web host computer, email server or router, acts autonomously under a global protocol. In the analogous electricity system every supply point, consumer and switching facility corresponds to a node.
The vision of the internet model is:
- “Every node in the electrical network of the future will be awake, responsive, adaptive, price-smart, eco-sensitive, real-time, flexible, humming - and interconnected with everything else” [Source: The Wired]
The internet enables many new opportunities. A conventional power station generates electricity in one location, using (usually) one type of generating technology and is owned by one legal entity. A virtual power station is a multi-fuel, multi-location and multi-owned power station.
Both stations supply energy reliably at predetermined times. Today this means making a power supply contract for each hour of the next day. The power stations must be able to change their power output quickly and sell this capability as ancillary services to the grid operator.
For a grid operator or energy trader, purchasing energy or ancillary services from a virtual power station is equivalent to purchasing from a conventional station. The concept of a virtual power station is not itself a new technology but a method of organising decentralised generation and storage in a way that maximises the value of the generated electricity to the utility. Virtual power stations using DG, RES and energy storage have the potential to replace conventional power stations step by step until a sustainable energy mix has developed. Extending this concept to a virtual utility merely extends the services available." (http://ec.europa.eu/research/energy/nn/nn_rt/nn_rt_dg/article_1158_en.htm)
New Rules website:
"In the early 20th century electricity generation and transmission technologies supported the idea that "big is better." As a result, regulatory rules encouraged the construction of centralized power plants and long distribution lines. In the 1990s the technological dynamic was reversed. Small power plants located closer to the customer were become increasingly competitive. This has occurred at the same time as most states, many cities, and the U.S. Congress are rewriting the rules that govern our electricity system. The challenge now is to write rules (i.e. codes, standards, regulations, statutes) that will encourage electricity customers to also become electricity producers." (http://www.newrules.org/electricity/producers.html)
"Distributed generation is another approach. It reduces the amount of energy lost in transmitting electricity because the electricity is generated very near where it is used, perhaps even in the same building. This also reduces the size and number of power lines that must be constructed.
Typical distributed power sources have low maintenance, low pollution and high efficiencies. In the past, these traits required dedicated operating engineers, and large, complex plants to pay their salaries and reduce pollution. However, modern embedded systems can provide these traits with automated operation and clean fuels, such as sunlight, wind and natural gas. This reduces the size of power plant that can show a profit.
The usual problem with distributed generators are their high costs." (http://en.wikipedia.org/wiki/Distributed_generation)
"In the era of electric deregulation customers have the ability to choose their electric supplier. But early indications are that the vast majority of consumers will choose not to choose. Who, then, should be their default supplier? In most states the incumbent utility has been given this huge pot of customers--only Massachusetts and Ohio have thus far decided that it should be the town or city who is responsible for serving these customers.
Community choice, or aggregation, will create community pools of electricity large enough to command leverage on the market, and with sufficient legal authority and financial flexibility to demand contracts from energy suppliers that satisfy local economic and environmental goals. In short, it places authority in the hands of those who will feel the impact of their decisions, making investment in renewable electricity much more likely." (http://www.newrules.org/electricity/default.html)
Technologies which would make it possible:
- Nanosolar: plastic solar panel manufacture: “Panel cost of manufacture is said to be $0.30 per watt. Panel cost at retail is around $1. Price of a machine which will print panels: $0.16 per panel per year.”
- Konarka Technologies: “thinks their panels will be about 1/3 the price of nanosolar. In about a year or so.”
- Jellyfish Wind Turbines: $400 a pop (see: Distributed Wind Power
From the Wikipedia:
"The one exception is probably microhydropower. A well-designed plant has nearly zero maintenance costs, and generates useful power indefinitely.
One favored source is solar panels on the roofs of buildings. These have high construction costs ($2.50/w, 2007). This is about fifty-fold higher than coal power plants ($0.047/w, 2007) and 40-fold higher than nuclear plants ($0.06/w, 2007). Most solar cells also have waste disposal issues, since solar cells often contain heavy-metal electronic wastes. The plus side is that unlike coal and hydropower, there are no pollution, mining safety or operating safety issues.
Another favored source is small wind turbines. These have low maintenance, and low pollution. Construction costs and total safety are also manyfold ($0.80/w, 2007) less per watt than large power plants, except in very windy areas. Wind towers and generators have substantial insurable liabilities caused by high winds, but good operating safety.
Distributed cogeneration sources use natural gas-fired microturbines or reciprocating engines to turn generators. The hot exhaust is then used for space or water heating, or to drive an absorptive chiller for air-conditioning. The clean fuel has only low pollution. Designs currently have uneven reliability, with some makes having excellent maintenance costs, and others being unacceptable.
Cogenerators are also more expensive per watt than central generators. They find favor because most buildings already burn fuels, and the cogeneration can extract more value from the fuel.
Some larger installations utilize combined cycle generation. Usually this consists of a gas turbine whose exhaust boils water for a steam turbine in a Rankine cycle. The condenser of the steam cycle provides the heat for space heating or an absorptive chiller. Combined cycle plants with cogeneration have the highest known thermal efficiencies, often exceeding 85%." (http://en.wikipedia.org/wiki/Distributed_generation)
Key Book to Read
Energy Autonomy. By Hermann Scheer
- Introduction, at http://ec.europa.eu/research/energy/nn/nn_rt/nn_rt_dg/article_1158_en.htm
- Key advantages, at http://ec.europa.eu/research/energy/nn/nn_rt/nn_rt_dg/article_1159_en.htm
- When consumers become producers, at http://www.newrules.org/electricity/producers.html . This site monitors regulatory progress in the U.S.
- Local and regional plans update, at http://www.newrules.org/electricity/planningfordg.html
- Course: the Distributed Generation Educational Module